Abstract
Primary ciliary dyskinesia (PCD) is a recessive heterogeneous disorder of motile cilia, affecting one per 15,000–30,000 individuals; however, the frequency of this disorder is likely underestimated. Even though more than 40 genes are currently associated with PCD, in the case of approximately 30% of patients, the genetic cause of the manifested PCD symptoms remains unknown. Because motile cilia are highly evolutionarily conserved organelles at both the proteomic and ultrastructural levels, analyses in the unicellular and multicellular model organisms can help not only to identify new proteins essential for cilia motility (and thus identify new putative PCD-causative genes), but also to elucidate the function of the proteins encoded by known PCD-causative genes. Consequently, studies involving model organisms can help us to understand the molecular mechanism(s) behind the phenotypic changes observed in the motile cilia of PCD affected patients. Here, we summarize the current state of the art in the genetics and biology of PCD and emphasize the impact of the studies conducted using model organisms on existing knowledge.
Highlights
The cilium is an ancient eukaryotic organelle, believed to be present in the last eukaryotic common ancestor (LECA) [1]
The measurements of the cilia beating using high-speed video-microscopy (HSVM), detection of marker proteins (e.g., DNAH5) using immunofluorescence microscopy and specific antibodies, and identification of the ultrastructural defects using transmission electron microscopy (TEM) in respiratory epithelial cells obtained from patients by nasal brush biopsy are other diagnostic tests that are conducted in the case of individuals with clinical symptoms to confirm cilia dysfunction
Based on the data obtained in green algae, it seems that the extent of the defects in the cilia ultrastructure that translates into cilia immotility and the severity of the Primary ciliary dyskinesia (PCD) symptoms in patients with mutated CCDC39 or CCDC40 genes is a consequence of the dysfunction of the mutated proteins as a determinant of the docking/positioning of three important ciliary complexes
Summary
The cilium is an ancient eukaryotic organelle, believed to be present in the last eukaryotic common ancestor (LECA) [1]. The immotile cilia are assembled as a single organelle (called the primary cilium) by non-dividing cells (G1 or G0 phase). Motile cilia are usually assembled as multiple structures They can perform sensory functions [8,9], but their primary role is to propel free-living organisms and sperm cells and to shift extracellular fluids and particles along the surface of the ciliated epithelial cells. Motile cilia are restricted to sperm cells (a single long cilium called the flagellum or sperm tail) and epithelial cells lining the nasal cavity, paranasal sinuses, middle ear, respiratory tracts, brain ventricles, and the Fallopian tube. The knowledge of the molecular basis of human ciliopathies has significantly advanced within the last several years Such progress would not be possible without the extensive analyses of the mechanisms controlling cilia assembly and function conducted using diverse model organisms. We emphasize and discuss the importance of studies conducted using model organisms in uncovering the molecular basis of the primary ciliary dyskinesia
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